Prevention of global warming has been an urgent issue in recent years, and all the aspects of society are requested to achieve power saving due to this reason. For example, an enormous amount of electric power is consumed for air conditioning in a factory, a large office building, an Internet data center or the like (hereinafter referred to as a “facility such as an office building”) and there are demands for both of power saving in such air-conditioning equipment and optimization of air conditioning.
In order to optimize air conditioning in a facility such as an office building, it is preferable to measure temperatures and humidities in many positions of the facility and to control air-conditioning equipment based on measurement results. When there are few measurement positions, a temperature sensor and a humidity sensor may individually be installed in the respective positions. The temperature sensor usable for this purpose may be a thermocouple, a platinum resistance temperature detector, a thermistor, an expansion thermometer, and the like. Meanwhile, the humidity sensor usable may be an electric resistance detection type humidity sensor, an electric capacitance detection type humidity sensor, and the like.
However, when the aforementioned sensors are used in many measurement positions, a large number of sensors are used, which leads to an increase in cost of the entire system. In the meantime, an increase in the number of sensors leads to an increase in cost for maintenance. In this regard, there is a proposal to measure a temperature in a facility such as an office building by use of a temperature measurement device employing an optical fiber as a temperature sensor (such a device will be hereinafter referred to as an “optical fiber temperature measurement device”).
The optical fiber temperature measurement device is configured to measure a temperature by inputting a laser beam into an optical fiber and detecting Raman scattered light generated inside the optical fiber. The device may measure temperature distribution in a longitudinal direction of the optical fiber within a short time.
Meanwhile, there is also a proposal to measure a humidity based on the principle of a typical wet-and-dry-bulb hygrometer by using an optical fiber temperature measurement device. A humidity measurement device of this type is configured to maintain a portion of an optical fiber in a moist state by continuously supplying water thereto and to calculate a relative humidity in an atmosphere by use of a difference between a temperature at a moist portion maintained in the moist state and a temperature at a dry portion.    Patent Document 1: Japanese Laid-open Patent Publication No. 02-171628    Patent Document 2: Japanese Laid-open Patent Publication No. 10-104363
The above-described humidity measurement device using the optical fiber is provided with a water tank and is configured to supply water from the water tank to the moist portion by means of a capillary action. However, in order to measure the humidity over a long time, it is preferably to perform an operation of checking whether the water is left in the water tank and refilling the water tank if the water is not left. When there are few measurement positions, it may be possible to check the water and to refill the water tank manually. However, when there are many measurement positions, it is difficult to check the water and to refill the water tank manually and equipment for automating the operation is used. Such automation may lead to an increase in size of a system and may result in an increase in cost of the entire system and an increase in cost for maintenance of the system.